Divergent growth response of Qinghai spruce to recent climate warming in the arid northeastern Tibet Plateau

Divergent responses of tree growth to climate change have been widely reported from the high altitude forests of the Northern Hemisphere. Here, we developed tree-ring width (TRW) and maximum latewood density (MXD) chronologies for the Qinghai spruce (Picea crassifolia) from three sites (DHS, XXG, and TLC) with different hydrothermal conditions in the arid northeastern Tibetan Plateau, and we used these chronologies to observe climategrowth relationships and divergent growth responses of the Qinghai spruce. Cross correlations showed highly significant divergences among the TRW and MXD chronologies. Precipitation was most strongly related to TRW in different spruce trees. At the upper treeline site (XXG) and at the relatively wet site (TLC), where growth was limited by temperature, MXD showed similar growth trends over time. At the dry site (DHS), TRW showed a strong drought stress signal over time, and MXD lost sensitivity to temperature variations. We would like to highlight the necessity for additional studies investigating possible non-stationary growth responses of trees that are experiencing climate warming, especially for studies of MXD at dry sites that are used for temperature reconstruction in arid areas.